Mobile wireless devices have evolved from providing analog circuit switched voice alone to offering a wide variety of digital services including voice, data and video that can be communicated through multiple different wireless networks. A “smart phone” mobile wireless device can provide many of these services through different mechanisms on different wireless networks, and a user of the mobile wireless device can expect similar quality of service whether provided through a circuit switched cellular connection, a packet switched cellular connection or a packet switched wireless local area network connection. Certain services can require high performance real-time quality of service characteristics to offer a suitable user experience, such as persistence of a connection for a voice call or a high quality frame rate for a video call. As the quality of a connection for a mobile wireless device can vary based on position of, interference received by and movement of the mobile wireless device and as several different connection points can be simultaneously available to the mobile wireless device, shifting an active connection between different connection points within or across wireless networks can impact quality of service. The shifting of connections between connection points can be referred to as handoff in cellular networks and as roaming in wireless local area networks. Cellular network handoff can be controlled by the cellular infrastructure, while wireless network roaming can be controlled by the mobile wireless device and in some cases by the wireless infrastructure.
Roaming in a wireless local area network can occur when a mobile wireless device moves its association from one access point to another access point in the wireless local area network. The mobile wireless device can determine when to search for alternative access points, what criteria to use to evaluate suitability of alternative access points to which to roam, and what thresholds to meet in order to roam to an alternative access point. Unlike handoff in cellular networks that can be specified in communication protocol standards and controlled by the cellular infrastructure, roaming in wireless local area networks can use proprietary methods executed in the mobile wireless device. The mobile wireless device can use a number of different performance criteria to determine when to roam among different access points in wireless local area networks. Access points can transmit and receive on one of several different radio frequency channels available in a radio frequency band, and different access points can use different radio frequency channels. The mobile wireless device can choose to switch between difference radio frequency channels used by the same access point or to a different access point.
In order to evaluate an alternative access point, the mobile wireless device can tune its own receiver to the transmitting radio frequency channel used by the alternative access point. While receiving signals transmitted by the alternative access point on a different radio frequency channel, the mobile wireless device can be unable to receive transmissions from a current access point to which the mobile wireless device is associated or connected. By interrupting current connections to roam, the search for alternative access points can affect data throughput performance between the mobile wireless device and the current access point. In addition, roaming can consume limited battery power when the mobile wireless device is associated with an access point but otherwise idle (i.e. not actively transmitting and receiving data). Roaming can require activating a transceiver in the mobile wireless device to search for alternative access points and processing any received signals. Adapting roaming properties to account for properties of a wireless network in which the mobile wireless device operates can improve both performance and power consumption to improve a user experience of the mobile wireless device.
A wireless local area network can be provided by a single access point such as in a home environment, by a few access points such as in a small office environment, or by numerous access points such as in a large enterprise office environment. Searching for and roaming to alternative access points can be adapted to the type of wireless local area network environment in which the mobile wireless device operates. Searching and roaming frequently in a home network in which no suitable alternative access points can exist can decrease data throughput and consume battery power unnecessarily. Searching and roaming infrequently in an enterprise network can result in suboptimal real time performance when signal strength can drop and switching between access points can be delayed. A single set of pre-determined roaming parameters for a variety of wireless local area network types can be less than ideal.
Thus there exists a need for methods and apparatuses to adapt roaming parameters for a mobile wireless device that can improve roaming in wireless networks.